German playmaker Ozil is expected to be sidelined for around a month, possibly even six weeks, with a grade two hamstring tear.

He joins Aaron Ramsey in the treatment room, with the Wales midfielder having seen his own comeback from a thigh injury ahead of Sunday's north London derby at Tottenham now put on hold.

"I am concerned that happens," Wenger said.

"If you look at our overall injury list going into such a final decisive part of the season, we have no (Jack) Wilshere, (Theo) Walcott, Ozil, Ramsey. We went to Bayern with no (Kieran) Gibbs or (Nacho) Monreal. Of course it is a concern," Wenger said.

"For some, like Walcott (knee injury), it is completely bad luck, the rest maybe we have to find out why it happened.

"We are analysing very deeply why it happened to see if there is a link between these injuries."

Ozil was substituted at half-time during Tuesday night's 1-1 draw against Bayern Munich in Germany, which followed on from an impressive display in what was his comeback after a recent break from action.

"He had a very good game against Everton on Saturday and I feel he was handicapped from early on in the game by this hamstring because I saw him stretching a few times," Wenger said.

"I told my physio 'is he all right because he looks to stretch his hamstring?' It looks to me that he played a long period in that first half being injured."

Wenger added: "I don't know for how long exactly he will be out, but it looks a minimum of three weeks.

"When the minimum is three weeks, the maximum is six.

"Honestly I am not specialist enough to know. It's a grade two hamstring (injury), (so) let's say four weeks."

Defender Gibbs is struggling to recover from a calf problem and Wilshere is sidelined by the fractured foot he suffered while on international duty with England.

Sweden midfielder Kim Kallstrom, though, could make his first appearance since signing on loan from Spartak Moscow now he has recovered from a back problem sustained before he joined on deadline day.

Wenger is confident the loss of Ozil will not prevent Arsenal getting their title challenge back on course at bitter rivals Tottenham on Sunday.

"It is a blow, of course, but I am confident we have the quality to deal without him during that period," said Wenger, whose side could be 10 points behind leaders Chelsea before they kick off at White Hart Lane.

"We have many creative players in our squad who can take over and produce quality performances.

"I am convinced that the team is ready, even without Ozil, to go for the challenge."

Following their FA Cup quarter-final win, the Gunners hold a match in hand on leaders Chelsea, but are seven points off top spot and currently in third place.

Wenger is expecting a focused display from his side in what will be a heated atmosphere.

"It has always been difficult at White Hart Lane, but we are in a position where of course we want to win the game, because after (losing at) Stoke, it is very important," Wenger said.

"We had a good result against Everton, we had a good result even at Bayern, but we must continue and have no more weak moments before the end of the season."